United States patent application Ser. No. 99,933, filed Dec. 3, 1979 in the names of Morris Berg, William Johnston and Carl Schaefer and assigned to the assignee of the present invention, discloses various forms of ceramic monolith porous wall filter elements for use as diesel exhaust particulate traps in the exhaust systems of diesel engines particularly those used in automotive vehicles. Tests have indicated such traps to be highly efficient means for trapping and retaining the carbonaceous particulates present in the exhaust gases of diesel engines. However, some difficulty has been encountered in attempting to regenerate or clean such filter elements by incineration of accumulated particulate deposits in situ merely through heating of the filter inlet gases as has been previously proposed.
The difficulty encountered in incineration of particulates in ceramic monolith filter elements appears to be that the temperature distribution of hot exhaust gases supplied to the element varies significantly within the inlet passages during the incineration process. This results in one area becoming clean before the others, thereby short circuiting the exhaust gas through the cleaned area and making it difficult to raise the remaining portion of the collected particulates to the incineration temperature. The problem is compounded by the heat insulating properties of the ceramic filter media which do not promote the conduction of heat from one area of the element to another. It is, thus, desired to provide improved means and methods for accomplishing incineration of particulates in ceramic monolith exhaust particulate traps for diesel engines and the like.